Electromechanical oscillator



Dec. 26, 1933. DESCH 1,941,445

ELECTROMECHANICAL OSCILLATOR Filed April 16, 1928 2 FIG. 1

ELI

50 tags.

Patented Dec. 26,1933

, UNITED sTA ms PA-TENT OFFICE 1 1,941,445 I AELECTROMECHANIOAL'OSCILLATOR V it noel Deisch, washingtomn. o. IApplicatio nrApril 16, 1928. Seria1'No. 270,54 6

10 Claims. (01. 250-36) My invention relates to electromechanicaloscillators, and has special reference to means of drive therefor.

The principal object of the invention, generally stated, is to providean electromechanical oscillator adapted to function either as anoscillation generator or as a resonator, in which a non-piezoelectricand non-magnetic body, whether insulating or conducting in nature,

10 may be used as theoscillating member.

' Another object of *the'invention is to provide an electromechanicaloscillator in which the driving force, is applied electrostaticallyrather than electromagnetically.

an electrostatically driven electromechanical oscillator bearingarmatures through one or, both of which the driving force is' applied,or'from either of which an electricalfrequency may be 20 obtained thatmay be used indirectly to effect the drive of the rod, or to controlcircuit. 1

Another object of the invention is to provide, in an oscillator havingelectrostatically operaan I associated 26 tive armatures, means wherebysaid armatures may be electrically charged to a desired potential.Another object of the invention is to provide a circuit arrangementsuitable for driving an oscillator electrostatically. I 30 Anotherobject of theinvention is to provide,

in an electromechanical oscillator driving system, means to set thejoscillating -member into oscillation from a condition of rest.

Developments in physics and especiallyinthe 135 electrical artshavebrought a demand for a source of timing impulses ofrigorousregularity, suitable for usein frequency control andfree quencymeasurement, and, in general, as a'ref- 1 from natural crystals, theirdimensions are limited by the size of available crystals, and theirform-is limited to that of a plate or slab, thislastffact making itdifficultin certain applications-to mount the oscillators to thebestadvan- Finally, the relatively high thermal dilatility of crystal quartzbrings a highertemperature change of frequency than is desirable.

By the present invention it becomes possible to employ any preferredelastic materialin the construction of an oscillator,as also touseshapes Another object of the invention is to provide better fitted toreduce harmonic vibrations and parasitic" damping, these combinedadvantages making posiblethe attainmentof a much higher constancy offrequency. As respects material, vitreous silica, for example, whichrepresents the closest approach among known materials to alternatingelectrostatic attraction" exerted on an armaure or armatures preferablyattached to the ends of the rod, by which energy is imparted.

tothe irod at each oscillation. Since the, frequency of vibration is inmost mases exceedingly high, corresponding. to a-high mean velocity ofapproach and recession of the armatures, and since on the other hand thelosses in the rod will usually be very small, the value of the forcethat must be brought to act on the electrodes to sustain theoscillations is correspondingly small.

In the drawing: Fig. 1 is a diagram of an oscillator incorporated in acircuit such as may-housed in effecting its drive.

Fig. 2 is an elevation of a rod-shaped oscillator and mounting, andshows a method of support ing the oscillator and its field electrodes. 1

Fig. 3 is atop plan'view of Fig. 2. Fig. 4 is a horizontal section onthe line 4, 4 of Fig. 2.

Referring now to Figs. 2,- 3, and '4, there is shown as an illustrativeformof the invention a preferably cylindrical rod 33, supported at itsnodal point by appropriate means, as by the clamp 34. At either end ofthe rod 33 are armatures-30, whichmay consist of thin conducting betweenthe armatures 30 and the lead 35 through theclamp 34. Adjacent thearmatures 30, and.

usually separated from them by only a very slight distance (e. g., circa0.02 cm) are the field electrodes 29, forming part of the yokes 28. Eachof the armatures 30 with its associated field electrocle 29 constitutesan electrostatic couple, the two elements of which are held in definiterelation by means of a suitable supporting structure, such as the spacerrods 26, the last being held securely in the central clamp 34 and theyokes 28, as shown. The armatures 30 are electrically isolated from thefield electrodes 29, as by the insulating bushings 27.

It will be obvious that if the electrodes 29 be connected, as throughthe leads 31, to a suitable coacting circuit producing electricaloscillations, the oscillating potential active on the field electrodes29 will cause these to become periodically charged, an opposite chargebeing at the same time periodically induced in the armatures 30. Thearmatures 30 will hence be periodically attracted. If the period of theoscillating force coincide with the natural period of the rod, therodwill be thrown into oscillation. It is thus apparent that the rod maybe applied as a frequency tester, controller, or stabilizer to anindependent circuit, acting in these several cases as a resonator.

When it is desired to employ the device as an oscillation generator therod, as is usual in the oscillator art, will be coupled into a properlya ranged coacting driving circuit, the oscillating rod reacting on theassociated circuit in such a way as to control the frequency of thecircuit, constraining this frequency to conform precisely to thefrequency of the rod. In the circuit shown by way of illustration inFig. 1 the driving energy to the rod 21, supported at 22, is shown asapplied through the armature 19, whereas the armature 23, in associationwith the field electrode 24, serves to control the frequency of thecircuit in a manner to be described. The armatures 19, 23, are connectedthrough conducting strips 20 and the lead 11 to one pole of a battery10, by which means they receive a permanent electric charge. The drivingfield electrode 18 has connection through the lead 13 to the secondary15 of the transformer 14 and to ground, whereas the electrode 24normally has connection through the lead 12 to the grid 9 of the triode8. The plate-filamentcircuit of the triode 8 in the position of theswitch 6 shown in full lines, comprises the battery 10 and the primary16 of the transformer 14.

Considering now the controlling action of the mechanical oscillator onthe circuit, it is evident that the armature 23 and its field electrode24 form a condenser whose capacity varies with the distance separatingtheir adjacent plates. One plate of this condenser (the armature 23 inthe present example) is charged to a given potential by the battery l0,as above noted. Battery 10 is connected across the filament and plate oftube 8, as shown. An electron discharge takes place through tube 8,resulting in a difference of potential being set up between the filamentand grid thereof, which potential is communicated to plate 23 throughleads 11 and 20 and to plate 24 through lead 12. With the rod inoscillation the charge active on the field electrode 24 will thusincrease as the armature 23 approaches electrode 24 and will decrease asthe armature recedes from electrode 24, the harmonic wave of potentialthus produced in electrode 24 being communicated to the conductor 12 andthrough it to the grid 9 of the triode 8. An amplified pulsating currentis thus produced in the filament-plate circuit of the triode 8 which,flowing through the primary 16 0f the transformer 14 induces analternating potential in the secondary 15 of said transformer. Thisalternating potential acts through the field electrode 18 on thearmature 19 (which, as before stated, is charged to a constant potentialof one sign) to cause an alternate attraction and repulsion in the same,thus serving to drive the rod. The potential of the battery 10 iscommunicated to plates 18 and 19 partly by direct metallic conductionand partly through electrostatic or condenser action, resulting in thefiow of a displacement current. The circuit comprises plate 19, leads 20and 11, battery 10, coils 16 and 15 of transformer 14, lead 13 and plate18. Mutual electrostatic action between coils 16 and 15 causes adisplacement current to fiow in the lead 13, placing plate 18 at adifferent potential from plate 19. An amount of lag is introduced intothe electrical oscillations in the course of their passage through thetransformer 14 which the purposes of the arrangement make desirable.

The starting i. e., the initiation of oscillations in the rod isaccomplished through an accessory component of the circuit, whichassociated component may be switched in when required. The drivingarmature 19 of the rod is thereupon supplied with a pulsating current ofapproximately the same frequency as the natural frequency of the rod,and this frequency is then varied until it attains the natural frequencyof the rod. When the applied frequency coincides with the naturalfrequency of the red, the latter is set into oscillation, and theelectrical connections may then be shifted so as to allow the rod tooperate automatically.

More particularly, to bring the auxiliary circuit into operation thebi-pole switch 6 is shifted to the position shown in dotted lines at 7.The grid 9 of the triode 8 is thus connected through the secondary 2 ofthe variable inductance coil 1 having the movable core 3 and to ground,the primary winding 4 of the coil 1 being at the same time put intoseries with the primary winding 16 of the transformer 14, and includedin the filament-plate circuit of the triode 8. With this arrangementcurrent is fed back from the coil 2 to the grid of the amplifying tube 8in the way usual in this type of oscillating circuit. The circuit willbegin to oscillate as soon as the double-throw switch is moved to theposition shown in dotted lines at 7. The constants of the coil 1 and theattached circuit are such that with the movable core 3 inserted theelectrical oscillations generated are of lower frequency than thenatural period of the rod. The frequency of oscillation is then raisedby slowly withdrawing the core 3 until the rod begins to oscillate,which condition will be indicated by a fall of voltage registered by thevoltmeter 5. The switch 6 will then be thrown to the position in whichit is shown in full lines, whereupon the rod will continue inoscillation automatically.

While I have described my invention in detail with respect to thepreferred form thereof, I do not desire to be limited to the formdescribed, since many changes or modifications may be made in this formwithout departing from the spirit and scope of my invention, and Idesire to cover all modifications and forms coming within the scope ofthe appended claims.

I claim:

1. An oscillator, comprising a body of vitreous material of low elastichysteresis and low temperature coefficient, armatures attached atantinodal points to said body, means whereby 2. An oscillator,comprising a rod of vitreous material of low elastic hysteresis and lowtemperature coefficient supported substantially at its nodal point,armatures attached atnon-nodal points to said rod, electrodes heldcontiguous to said armatures, and a source of oscillating potential tosupply energy to drive said rod.

3. An oscillator, comprising a rod of vitreous material of low elastichysteresis; and low tem-- perature coefficient supported at its'nodalpoint, conducting plates attached at antinodes vto'said rod, means toconnectsaid conducting plates to a source of potential, other'conductingplates held in close approximation to said electrodes,

and an oscillation generator to supply energy to drive said rod. I

4. An oscillator, comprising a rod of vitreous material of low elastichysteresis and low temperature coeincient supported at its nodal point,flat conducting plates, here called armatures, attached at opposite endsof said rod, conductors extending along said rod to connect saidarmatures to a source of electric potential, conducting plates, herecalled field pieces, held in close proximity to said armatures, anoscillation generator, to supply energy to n-1 of said field pieces todrive said rod, and a relay system coupled to one of said field'piecesto control said frequency generator. y p

5. In electromechanical oscillators. a, vitreous elastic body of lowtemperature coeflicient, means to support said body at a point allowingsymmetrical longitudinal oscillation thereof, conducting armaturessecured to said body, conductingleads to connect said armatures" to asource or electrical energy, electrodes held in proximity to saidarmatures, conducting leads to connect said electrodes to a source ofelectrical energy, and structural means coupling said oscillatorsupporting means and said electrodes to hold said armatures and saidelectrodes in a desired spatial relation.

6. In an electromechanical oscillator electrically coupled to anelectrical oscillation generator supplying driving energy to saidoscillator, and including means normally controlled by said oscillatorfor controlling the frequency of the oscillations produced by saidoscillation generator; means for producing oscillations insaidoscillation generator independently of the controlling action ofsaidoscillator, and means for bringing the frequency of theseindependently produced oscillations to the natural frequency of saidoscillator to bring said oscillator into oscillation from a state ofrest. 7. In an electromechanical oscillator electrically coupled to acircuit supplying driving energy to said oscillator, and including meansby which the frequency of the output of said circuit is during thenormal operation of said oscillator controlled by said oscillator; meansto alter the said circuit self-oscillating, andmeans to bring thenatural electricalperiod of said self -oscillat- ,ing circuit tosubstantial coincidence with the natural mechanical period of saidoscillator.

8. An electromechanical oscillator, comprising a rod of silica, a framefor supporting said rod said plates, and meansfor connecting said platesand said yokes to a source of periodically varyin electric force. I

9. An electromechanical oscillator, comprising ,electricalcharacteristicsof said circuit to make a silica rod having metal platesmounted on its ends, a frame including side bars, middle and end yokes,the middle yoke being clamped to the mid-' section of said rod and theend yokes in close proximity to said plates and insulated from said sidebars, a conductor connecting said platesto the middle yoke and means forconnecting the several yokes to a source of periodically varyingelectric force. I

10. A body of vitreous material of low elastic hysteresis and lowtemperature coefficient capable of oscillation, armatures attached tosaid body, and'means to act on one of said armatures electrostaticallyto cause said body to oscillate.

NOEL DEISCH.

